The ultimate objective of the current proposal is to obtain data which can be used to evaluate the present or potential role of antioxidants as inhibitors of chemical carcinogens in the environment. An initial objective is to elucidate the mechanism or mechanisms of inhibition of polycyclic hydrocarbon induced neoplasia by butylated hydroxyanisole, butylated hydroxytoluene and ethoxyquin. In vivo studies of the effects of the three antioxidants on carcinogenesis induced by dibenz(a,h) anthracene, 3-methylcholanthrene and their K- region epoxides will be carried out along with comparable studies of 7,12-dimethylbenz(a) anthracene and several of its derivatives. In vitro studies of binding of carcinogens or their metabolites to the antioxidants will be performed in simple solutions and also under conditions of microsomal mixed functional oxidase activity. A second objective is to determine the conditions under which antioxidants inhibit carcinogenesis in vivo and the chemical classes of carcinogen that can be inhibited. Studies aimed at determining the chemical characteristics of antioxidants which control their ability to inhibit chemical carcinogenesis are also planned.